1. Field of the Invention
The present invention relates to a semiconductor integrated circuit, and more particularly, to a liquid crystal display (LCD) or panel driving apparatus with a self-masking function.
2. Description of the Related Art
A liquid crystal panel displays image data using a matrix of pixels, each located at an intersection of a gate line and a source line. Each pixel includes a liquid crystal cell that adjusts the amount of light transmission according to the image data, and a thin film transistor that transmits the image data from a source line to the liquid crystal cell. A liquid crystal panel module includes a gate driver and a source driver that respectively drive the gate line and the source line.
FIG. 1 illustrates the power-on sequence timing of a conventional liquid crystal panel module. Referring to FIG. 1, a first supply voltage VDD1 and a second supply voltage VDD2 output from a source driver are supplied at a point of time t1. The first supply voltage VDD1 is a voltage for driving a logic circuit of the source driver, and the second supply voltage VDD2 is a high voltage for driving the source driver. Both the first supply voltage VDD1 and the second supply voltage VDD2 are stabilized at a point of time t2. A timing controller transmits image data to the source driver after several frames a reset signal RESET output from the timing controller that controls the liquid crystal panel module transitions from a logic low level to a logic high level. A horizontal start pulse signal TP output from the timing controller that drives source lines of a liquid crystal panel, and signals output from the source driver that correspond to the image data are supplied at a point of time t3.
The horizontal start pulse signal TP, which controls switches that transmit the signals output from the source driver to the source lines, turns on the switches at logic low. The horizontal start pulse signal TP that goes low is supplied between the points of time t1 and t3 before the signals output from the source driver are supplied and, thus, unknown signals output from the unstable source driver are transmitted to the source lines. Thus, stripes appear on the liquid crystal panel during an initial power-on stage, causing a display failure as illustrated in FIG. 2. The display state of the liquid crystal panel returns to a normal state at the point of time t3 after several tens of milliseconds.
Accordingly, there is a growing need for a method of preventing unknown image data from being displayed on the liquid crystal panel during the initial power-on stage.